1. Technological Field
The present invention relates to an image forming apparatus.
2. Description of the Related Art
Conventionally known electrophotographic image forming apparatuses develop an electrostatic latent image formed on a photoreceptor with toner to form a toner image, transfer the formed toner image on a sheet (a transfer medium) at a transfer device, and thermally fix the transferred toner image to form an image on the sheet.
Some of such image forming apparatuses are provided with a separation claw which contacts with the photoreceptor and separates the sheet from the photoreceptor as an separation assisting unit when separation property of the sheet from the photoreceptor is deteriorated at the transfer device. Multiple separation claws are arranged along the axial direction of the photoreceptor and pressurized by a spring. The separation claws are configured to contact with or separate from the photoreceptor according to the timing of sheet conveyance by a contact/separation mechanism.
According to a technique regarding the above-described contact/separation mechanism, the separation claw contacts with the photoreceptor on the basis of the concentration data at the tip of the output image, only when separation defects occur at a high probability (for example, see Japanese Patent Application Laid-Open Publication No. 2001-337563).
According to another technique, the separation claws contact with the photoreceptor on the basis of humidity, weight of the sheet, and the like, only when the separation defects occur at a high probability (for example, see Japanese Patent Application Laid-Open Publication No. hei 7-92819).
However, since the techniques according to Japanese Patent Application Laid-Open Publication Nos. 2001-337563 and hei7-92819 aim at suppressing damages of the photoreceptor or abrasion of the separation claw, contact/separation of the separation claw is frequently repeated so that problems are caused regarding durability of the contact/separation mechanism, such as abrasion of a cam member. Although the problems regarding durability can be solved by changing the contact/separation mechanism for another, new problems are caused in turn, such as large cost, complication of the apparatus, and the like.